Christmas tree



FIG. 1 is a perspective view of a Christmas tree showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The star, ornaments and small circles on the edges of the branches are shown in broken lines and do not form part of the claimed design. 

The ornamental design for a Christmas tree, as shown and described. 